WO1995023566A1 - Acetabular cup - Google Patents
Acetabular cup Download PDFInfo
- Publication number
- WO1995023566A1 WO1995023566A1 PCT/GB1995/000403 GB9500403W WO9523566A1 WO 1995023566 A1 WO1995023566 A1 WO 1995023566A1 GB 9500403 W GB9500403 W GB 9500403W WO 9523566 A1 WO9523566 A1 WO 9523566A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- socket
- acetabular cup
- radius
- point
- curvature
- Prior art date
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Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2/32—Joints for the hip
- A61F2/34—Acetabular cups
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2/32—Joints for the hip
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
- A61F2002/30621—Features concerning the anatomical functioning or articulation of the prosthetic joint
- A61F2002/30649—Ball-and-socket joints
- A61F2002/30654—Details of the concave socket
- A61F2002/30655—Non-spherical concave inner surface
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
- A61F2002/30621—Features concerning the anatomical functioning or articulation of the prosthetic joint
- A61F2002/30649—Ball-and-socket joints
- A61F2002/30654—Details of the concave socket
- A61F2002/30655—Non-spherical concave inner surface
- A61F2002/30657—Non-spherical concave inner surface made of different partially-spherical concave portions
- A61F2002/30658—Non-spherical concave inner surface made of different partially-spherical concave portions having a central conforming area surrounded by a peripheral annular non-conforming area
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
- A61F2002/30667—Features concerning an interaction with the environment or a particular use of the prosthesis
- A61F2002/30673—Lubricating means, e.g. synovial pocket
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
- A61F2002/30667—Features concerning an interaction with the environment or a particular use of the prosthesis
- A61F2002/30682—Means for preventing migration of particles released by the joint, e.g. wear debris or cement particles
- A61F2002/30685—Means for reducing or preventing the generation of wear particulates
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2/30767—Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
- A61F2002/30934—Special articulating surfaces
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2/32—Joints for the hip
- A61F2002/3225—Joints for the hip the diameter of the inner concave femoral head-receiving cavity of the inner acetabular shell being essentially greater than the diameter of the convex femoral head
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2/32—Joints for the hip
- A61F2/34—Acetabular cups
- A61F2002/3453—Acetabular cups having a non-hemispherical convex outer surface, e.g. quadric-shaped
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
- A61F2/02—Prostheses implantable into the body
- A61F2/30—Joints
- A61F2/32—Joints for the hip
- A61F2/36—Femoral heads ; Femoral endoprostheses
- A61F2/3609—Femoral heads or necks; Connections of endoprosthetic heads or necks to endoprosthetic femoral shafts
- A61F2002/3611—Heads or epiphyseal parts of femur
Definitions
- This invention relates to an acetabular cup and to a prosthetic hip joint consisting of the acetabular cup and a femoral component.
- the invention relates to such a joint having improved lubrication qualities.
- the smaller radial clearances are used for hard on hard prostheses, such as metal on metal and ceramic on ceramic, with larger clearances being used for cushion form bearings.
- polyethylene R x - R 2 is between 0.01 and 0.03mm.
- an acetabular cup having a concave bearing socket adapted to receive the head of the femoral component of a hip prosthesis, in which the radius of curvature of the surface of the socket continuously and monotonically decreases from the lip of the socket to a minimum R 2 at a point within the socket.
- the acetabular cup according to the invention provides distinct advantages when used in conjunction with a standard femoral component having a substantially spherical head when R 2 is no greater than the radius of the spherical head of the femoral component R x .
- R j When R j is greater than R 2 , the bearing still fits together by virtue of this continuous monotonic increase in the radius of curvature as the lip of the socket is approached, but importantly a pool of lubricating fluid is trapped at the pole of the socket.
- Both these arrangements contribute to more effective "squeeze film lubrication" which occurs when load is applied to the joint and a film of lubricating fluid is squeezed between the two components. They also both act to spread the applied load more effectively over the surfaces of the components, either over a large contact area towards the pole or over a contact area spaced from and distributed around the pole.
- the surface of the socket approximates that of a sphere at the point of minimum radius of curvature.
- R 2 is equal to R 1 . This ensures that there is a large contact area between the femoral head and the acetabular cup socket as discussed previously.
- the surface of the socket coincides with that of a sphere at the intersection of the surface of the socket with a plane.
- R 2 be less than R x and that the radius of the sphere with which the surface of the socket coincides at the intersection of the surface of the socket with the plane be equal to R-_ .
- an annular contact ring may be formed between the socket and the head which traps lubricating fluid between the two towards the point of minimum radius of curvature.
- Both of the above preferred conditions may be satisfied in a single socket by arranging for the surface of the socket to be a surface of revolution about the normal to the surface at the point of minimum radius of curvature.
- Figure 1 illustrates a conventional sphere on sphere prosthetic hip joint
- Figure 2 illustrates a joint according to the invention where R x is greater than R 2 ;
- Figure 3 illustrates a joint according to the present invention where R ⁇ equals R 2 ;
- Figure 4 illustrates a particular geometry of the acetabular cup. Detailed description
- Figure 1 illustrates a conventional sphere on sphere prosthetic hip joint.
- the joint consists of an acetabular cup 10 and a spherical head 12 of a femoral component.
- the cup 10 includes a socket with a spherical concave surface 14 and the surface of the spherical head 12 is referenced 16.
- the radius R x of the surface 16 is 9.8mm and the radius R 2 of the surface 14 is 10mm, giving a difference of 0.2mm. This difference affords a clearance 20 between the two components of the joint and lubricating fluid is able to penetrate between the two within this clearance.
- the two radii R x and R 2 are selected to be close to one another, thereby reducing to a minimum the amount of play in the joint. As a result, the squeeze film lubrication performance of this joint is relatively poor.
- FIG. 2 illustrates an embodiment of the present invention in which R x is greater than R 2 .
- the joint consists of an acetabular cup 10 and the spherical head 12 of a femoral component.
- the surface of the spherical head is referenced 16.
- the surface 14 of the socket in the acetabular cup 10 is defined by an "alpharabola".
- the use of the alpharabola as the geometry of the socket allows the rate of change of the curvature of the surface to be varied continuously over the surface and this rate of change can be determined with a single parameter ⁇ , once the desired minimum curvature is known.
- the alpharabola geometry is described by:
- R 2 is the desired minimum radius of curvature
- x is a Cartesian co-ordinate representing distance from the point of minimum radius of curvature along the normal to the surface at that point;
- y and z are the remaining Cartesian co ⁇ ordinates.
- R 2 is 10mm and the parameter ⁇ is selected to be 0.5.
- the radius R x of the head 12 is 10.5mm.
- a pool of fluid 22 is trapped at the pole of the alpharabola and there is an annular contact ring 24 between the two surfaces 14, 16 which serves to trap the fluid.
- the decreasing radius of curvature of the surface 14 of the cup 10 as one approaches the rim ensures that the two surfaces 14, 16 define a relatively large clearance 20 at the rim of the cup. This facilitates the ingress of lubricating fluid.
- Figure 3 illustrates a joint according to the invention in which R ⁇ is equal to R 2 at 10mm.
- the parameter a is selected to be 0.5.
- the parameter ⁇ can be selected according to the circumstances, but is necessarily less than unity. Usually, ⁇ will be greater than 0 and preferably lies between 0.5 and 0.9. Values of ⁇ close to unity will in general be selected for metal on metal or ceramic components. Intermediate values will be chosen for polyethylene cups and lower values for cushion form bearings. The difference R : - R 2 will normally be selected to lie between 0 and 1mm.
- the axis of symmetry of the alpharabola need not coincide with the polar axis of the cup, ie. need not be normal to the rim 28 of the cup 10.
- the point of minimum radius of curvature, referenced 30 will be positioned so that the normal to the surface at that point coincides with the direction at which load on the joint will predominantly be applied.
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- Health & Medical Sciences (AREA)
- Orthopedic Medicine & Surgery (AREA)
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- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- Vascular Medicine (AREA)
- Life Sciences & Earth Sciences (AREA)
- Cardiology (AREA)
- Oral & Maxillofacial Surgery (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Prostheses (AREA)
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Abstract
A prosthetic joint is described consisting of an acetabular cup (10) and a femoral component having a spherical head (12) of radius R1. The surface (14) of the socket in the acetabular cup (10) is defined by an 'alpharabola'. The alpharabola geometry is described by: αx?2 + y2 + z2 = 2R¿2x, 0 < α < 1, where R2 is the desired minimum radius of curvature; x is a Cartesian coordinate representing distance from the point of minimum radius of curvature (30) along the normal to the surface at that point; and y and z are the remaining Cartesian coordinates. The alpharabola surfaces are surfaces of revolution about the x axis. When R2 is less than R1, a pool of fluid (22) is trapped at the pole of the apharabola and there is an annular contact ring (24) between the two surfaces (14, 16) which serves to trap the fluid. When R1 is equal to R2, in place of an annular contact ring (24), there is an enlarged contact area (26). Both arrangements contribute to more effective squeeze film lubrication and less wear on the two components (10, 12).
Description
ACETABULAR CUP
This invention relates to an acetabular cup and to a prosthetic hip joint consisting of the acetabular cup and a femoral component. In particular, the invention relates to such a joint having improved lubrication qualities.
Background to the invention
Over half a million artificial hip joints are implanted in patients every year. These are all ball and socket joints with a spherical femoral head and a hemispherical acetabular cup or socket. Over 95% of these comprise a hard metal or ceramic head, with an ultra-high molecular weight polyethylene cup. Other types include metal on metal and ceramic on ceramic and, more recently, soft or compliant bearing surfaces, termed "cushion form bearings". All these joints have a primarily spherical geometry with the radius of curvature of the head Rx being smaller than the radius of curvature of the socket R2. This allows the joint to be assembled and free to move. Typically, the radial clearance R2 - Ri is between 0.05 and 0.5mm. The smaller radial clearances are used for hard on hard prostheses, such as metal on metal and ceramic on ceramic, with larger clearances being used for cushion form bearings. For commonly used polyethylene Rx - R2 is between 0.01 and 0.03mm. Typically, when the two spheres come into contact at a point the materials then deform elastically with the contact area increasing as the load and contact stress increase. The radial clearance and the elasticity of the materials determine the contact area, stress and lubricating film thickness, all of which determine the wear of the materials.
In hard on hard and cushion form bearings, there are real concerns about high levels of friction at start up after periods of high constant load when the lubricating film has been squeezed out from between the two joint components. It has been proposed in metal on metal joints to form a dimple or local discontinuity in the surface of the cup at the pole.
in an attempt to trap the fluid and reduce friction. It is not clear whether this works, but it has been established that the dimple produces discontinuities in the stress field.
It is an object of this invention to provide a prosthetic hip joint with improved lubrication and reduced wear.
Summary of the invention
According to the present invention, there is provided an acetabular cup having a concave bearing socket adapted to receive the head of the femoral component of a hip prosthesis, in which the radius of curvature of the surface of the socket continuously and monotonically decreases from the lip of the socket to a minimum R2 at a point within the socket. The acetabular cup according to the invention provides distinct advantages when used in conjunction with a standard femoral component having a substantially spherical head when R2 is no greater than the radius of the spherical head of the femoral component Rx. When R2 is equal to Rl f there is no single point of contact between the spherical head and the acetabular cup, but rather an enlarged contact area through which more uniform pressure is applied under load. Furthermore, since towards the lip of the socket the radius of curvature increases - and hence the amount of curvature decreases - a larger space is defined between the socket and the head than would be the case with two spherical components.
When Rj is greater than R2, the bearing still fits together by virtue of this continuous monotonic increase in the radius of curvature as the lip of the socket is approached, but importantly a pool of lubricating fluid is trapped at the pole of the socket. Both these arrangements contribute to more effective "squeeze film lubrication" which occurs when load is applied to the joint and a film of lubricating fluid is squeezed between the two components. They also both act to spread the applied load more effectively over the surfaces of the components, either over a large contact area towards the pole or over a contact area spaced from and distributed around the pole.
Preferably, the surface of the socket approximates that of a sphere at the point of minimum radius of curvature. In these circumstances, it is preferred that R2 is equal to R1. This ensures that there is a large contact area between the femoral head and the acetabular cup socket as discussed previously.
Alternatively or additionally, it is preferred that the surface of the socket coincides with that of a sphere at the intersection of the surface of the socket with a plane. In these circumstances, it is also preferred that R2 be less than Rx and that the radius of the sphere with which the surface of the socket coincides at the intersection of the surface of the socket with the plane be equal to R-_ . In this way, an annular contact ring may be formed between the socket and the head which traps lubricating fluid between the two towards the point of minimum radius of curvature.
Both of the above preferred conditions may be satisfied in a single socket by arranging for the surface of the socket to be a surface of revolution about the normal to the surface at the point of minimum radius of curvature.
Brief description of the drawings
The present invention will now be described by way of example with reference to figures 1 to 3 of the accompanying drawings in which:
Figure 1 illustrates a conventional sphere on sphere prosthetic hip joint;
Figure 2 illustrates a joint according to the invention where Rx is greater than R2;
Figure 3 illustrates a joint according to the present invention where Rλ equals R2; and
Figure 4 illustrates a particular geometry of the acetabular cup.
Detailed description
Figure 1 illustrates a conventional sphere on sphere prosthetic hip joint. The joint consists of an acetabular cup 10 and a spherical head 12 of a femoral component. The cup 10 includes a socket with a spherical concave surface 14 and the surface of the spherical head 12 is referenced 16. In the example illustrated, the radius Rx of the surface 16 is 9.8mm and the radius R2 of the surface 14 is 10mm, giving a difference of 0.2mm. This difference affords a clearance 20 between the two components of the joint and lubricating fluid is able to penetrate between the two within this clearance.
When the joint is placed under load, initial contact between the two surfaces 14, 16 occurs at a point 18. As the load is increased, surface deformation will cause the contact area to spread until the elastic restoring forces are equal to the applied load.
Because the predominant movement of the natural hip joint is one of rotation about the femoral head, the two radii Rx and R2 are selected to be close to one another, thereby reducing to a minimum the amount of play in the joint. As a result, the squeeze film lubrication performance of this joint is relatively poor.
Figure 2 illustrates an embodiment of the present invention in which Rx is greater than R2. The joint consists of an acetabular cup 10 and the spherical head 12 of a femoral component. The surface of the spherical head is referenced 16. In this case, the surface 14 of the socket in the acetabular cup 10 is defined by an "alpharabola". The use of the alpharabola as the geometry of the socket allows the rate of change of the curvature of the surface to be varied continuously over the surface and this rate of change can be determined with a single parameter α, once the desired minimum curvature is known. This allows the position and size of the contact area on the head 12 and cup 10 to be varied, permitting pools of lubricating fluid 22 to be trapped in the contact to assist lubrication. In addition, the need for a
radial clearance between the head 12 and the cup 10 is avoided.
The alpharabola geometry is described by:
αx2 + y2 + z2 = 2R2x
0 < α < 1
where: R2 is the desired minimum radius of curvature;
x is a Cartesian co-ordinate representing distance from the point of minimum radius of curvature along the normal to the surface at that point; and
y and z are the remaining Cartesian co¬ ordinates.
All these geometries are symmetrical about the x axis, ie. about the normal to the surface at the point of minimum radius of curvature, and this ensures that the alpharabola surfaces are surfaces of revolution about the x axis.
In figure 2, R2 is 10mm and the parameter α is selected to be 0.5. The radius Rx of the head 12 is 10.5mm. As can be seen, a pool of fluid 22 is trapped at the pole of the alpharabola and there is an annular contact ring 24 between the two surfaces 14, 16 which serves to trap the fluid. In addition, the decreasing radius of curvature of the surface 14 of the cup 10 as one approaches the rim ensures that the two surfaces 14, 16 define a relatively large clearance 20 at the rim of the cup. This facilitates the ingress of lubricating fluid.
Figure 3 illustrates a joint according to the invention in which Rτ is equal to R2 at 10mm. Again, the parameter a is selected to be 0.5. As can be seen, there is again a relatively large clearance 20 between the two surfaces 14, 16 towards the rim of the cup, but in place of an annular contact
ring 24, there is an enlarged contact area 26. Again, this contributes to more effective squeeze film lubrication and less wear on the two components. The reduction in wear is important, since it in turn reduces the amount of debris in the joint, which debris can cause unwanted reaction in the surrounding tissue.
The parameter α can be selected according to the circumstances, but is necessarily less than unity. Usually, α will be greater than 0 and preferably lies between 0.5 and 0.9. Values of α close to unity will in general be selected for metal on metal or ceramic components. Intermediate values will be chosen for polyethylene cups and lower values for cushion form bearings. The difference R: - R2 will normally be selected to lie between 0 and 1mm.
As can be seen from figure 4, the axis of symmetry of the alpharabola need not coincide with the polar axis of the cup, ie. need not be normal to the rim 28 of the cup 10. The point of minimum radius of curvature, referenced 30 will be positioned so that the normal to the surface at that point coincides with the direction at which load on the joint will predominantly be applied.
Claims
1. An acetabular cup having a concave bearing socket adapted to receive the head of the femoral component of a hip prosthesis, in which the radius of curvature of the surface of the socket continuously and monotonically decreases from the lip of the socket to a minimum R2 at a point within the socket.
2. An acetabular cup according to claim 1 in which the surface of the socket approximates that of a sphere at the said point.
3. An acetabular cup according to claim 1 in which the surface of the socket approximates that of a sphere at the intersection of the surface of the socket with a plane.
4. An acetabular cup according to claim 2 or claim 3 in which the surface of the socket is a surface of revolution about the normal to the surface at the said point of minimum radius of curvature.
5. An acetabular cup according to claim 4 in which the surface of revolution is defined by the following relationship:
ax2 + y2 + z2 = 2R2x
0 < α < 1
where: x is a Cartesian coordinate representing distance from the said point along the said normal; and
y and z are the remaining Cartesian coordinates.
6. An acetabular cup according to claim 5 in which:
0.5 < α < 0.9.
7. A hip prosthesis comprising an acetabular cup according to any preceding claim and a femoral component having a substantially spherical head, the concave bearing socket being adapted to receive the head of the femoral component, in which R2 is no greater than the radius of the spherical head of the femoral component Rx.
8. A hip prosthesis according to claim 7 in which R2 is equal to Rx and the surface of the socket approximates that of a sphere of radius Rx at the said point.
9. A hip prosthesis according to claim 7 in which R2 is less than Rx and the surface of the socket approximates that of a sphere of radius R.^ at the intersection of the surface of the socket with a plane.
10. A hip prosthesis according to claim 9 in which:
0 ≤ R1 - R2 ≤ 1mm.
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP95909061A EP0748193B1 (en) | 1994-03-03 | 1995-02-27 | Acetabular cup |
DE69524395T DE69524395T2 (en) | 1994-03-03 | 1995-02-27 | HIP PAN |
AT95909061T ATE209880T1 (en) | 1994-03-03 | 1995-02-27 | HIP JOINT POCKET |
DK95909061T DK0748193T3 (en) | 1994-03-03 | 1995-02-27 | Hip bowl-like cup |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9404077A GB9404077D0 (en) | 1994-03-03 | 1994-03-03 | Acetabular cup |
GB9404077.1 | 1994-03-03 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1995023566A1 true WO1995023566A1 (en) | 1995-09-08 |
Family
ID=10751212
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1995/000403 WO1995023566A1 (en) | 1994-03-03 | 1995-02-27 | Acetabular cup |
Country Status (8)
Country | Link |
---|---|
EP (1) | EP0748193B1 (en) |
AT (1) | ATE209880T1 (en) |
DE (1) | DE69524395T2 (en) |
DK (1) | DK0748193T3 (en) |
ES (1) | ES2167416T3 (en) |
GB (1) | GB9404077D0 (en) |
PT (1) | PT748193E (en) |
WO (1) | WO1995023566A1 (en) |
Cited By (21)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1997016138A1 (en) * | 1995-11-02 | 1997-05-09 | Wright Medical Technology, Inc. | Low-wear ball and cup joint prosthesis |
WO1997016137A1 (en) * | 1995-10-31 | 1997-05-09 | Sarkisian James S | Prosthetic joint and method of manufacture |
WO1997038650A1 (en) * | 1996-04-12 | 1997-10-23 | Sulzer Orthopädie Ag | Artificial joint, particularly an artificial hip joint |
US5928285A (en) * | 1997-05-30 | 1999-07-27 | Bristol-Myers Squibb Co. | Orthopaedic implant having an articulating surface with a conforming and translational surface |
WO2002043626A1 (en) | 2000-12-01 | 2002-06-06 | Depuy International Limited | An orthopaedic joint prosthesis |
AU755807B2 (en) * | 1998-11-05 | 2002-12-19 | Louis U. Bigliani | Orthopaedic implant having an articulating surface with a conforming and translational surface |
US6610097B2 (en) | 2000-03-15 | 2003-08-26 | Depuy Orthopaedics, Inc. | Prosthetic cup assembly which includes components possessing self-locking taper and associated method |
EP1767171A1 (en) * | 2005-09-23 | 2007-03-28 | Benoist Girard Sas | Prosthetic joints |
US7326253B2 (en) | 2001-11-16 | 2008-02-05 | Depuy Products, Inc. | Prosthetic cup assembly having increased assembly congruency |
FR2904930A1 (en) * | 2006-08-18 | 2008-02-22 | Advanced Technical Fabrication | Double mobility acetabulum cup for hip prosthesis, has metallic inserting cup limited by hemispherical concave receiving surface that presents roughness parameter and out-of roundness, which are lower than specific micrometers |
EP1952786A3 (en) * | 2007-02-05 | 2008-08-13 | Depuy Products, Inc. | Aspherical hip bearing couple |
WO2008102014A1 (en) * | 2007-02-23 | 2008-08-28 | Ceramtec Ag | Reduction of the development of stripe wear on inserts for hip joint prostheses by modifying the geometry of the transition between the face and spherical recess |
US7469474B2 (en) | 2002-01-17 | 2008-12-30 | Depuy International Limited | Manufacturing a component with a near spherical surface |
EP2108337A3 (en) * | 2001-12-19 | 2010-08-04 | Depuy Orthopaedics, Inc. | Prosthetic joints having reduced area bearing surfaces and application thereof to a range of sizes of prosthetic joints |
US7985262B2 (en) | 2007-12-28 | 2011-07-26 | Depuy Products, Inc. | Aspheric hip bearing couple |
US9005306B2 (en) | 2006-11-07 | 2015-04-14 | Biomedflex, Llc | Medical Implants With Compliant Wear-Resistant Surfaces |
US9005307B2 (en) | 2006-11-07 | 2015-04-14 | Biomedflex, Llc | Prosthetic ball-and-socket joint |
US9107754B2 (en) | 2006-11-07 | 2015-08-18 | Biomedflex, Llc | Prosthetic joint assembly and prosthetic joint member |
US9445904B2 (en) | 2009-07-14 | 2016-09-20 | Biomet Manufacturing, Llc | Multiple bearing acetabular prosthesis |
US9445903B2 (en) | 2008-11-24 | 2016-09-20 | Biomet Manufacturing, Llc | Multi-bearing acetabular prosthesis |
US9566157B2 (en) | 2006-11-07 | 2017-02-14 | Biomedflex, Llc | Three-member prosthetic joint |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
ES2430199T3 (en) | 2006-03-20 | 2013-11-19 | Smith & Nephew, Inc. | Acetabular cup set for multiple support materials |
WO2008058756A2 (en) * | 2006-11-17 | 2008-05-22 | Scyon Orthopaedics Ag | Wear-reducing geometry of articulations in total joint replacements |
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FR2134170A1 (en) * | 1971-04-23 | 1972-12-08 | Benoist Girard & Cie | |
FR2315903A1 (en) * | 1975-06-18 | 1977-01-28 | Sulzer Ag | ARTIFICIAL GLENOID CAVITY |
DE2742464A1 (en) * | 1977-09-21 | 1979-03-22 | Pfaudler Werke Ag | Internal body joint prosthesis - has socket sliding on ball on circular line of socket of larger radius |
FR2413078A1 (en) * | 1978-01-03 | 1979-07-27 | Serole Michelle | Hip prosthesis made of composite materials - has low wt. which assists swimming and can also be used for other body joints |
WO1986001394A1 (en) * | 1984-08-28 | 1986-03-13 | Rob. Mathys Co. | Artificial articular cavity for the hip with hydrostatic head support |
EP0226762A1 (en) * | 1985-11-18 | 1987-07-01 | GebràDer Sulzer Aktiengesellschaft | Artificial acetabular cup |
DE3630276A1 (en) * | 1986-09-05 | 1988-03-17 | Gernot Dr Med Felmet | Cementlessly implantable self-tensioning acetabular cup |
EP0302850A2 (en) * | 1987-07-09 | 1989-02-08 | Menschik, Alfred, Dr.med. | Artificial hip joint |
DE3840468A1 (en) * | 1988-12-01 | 1990-06-07 | Lieke Michael | Endoprosthetic components for an acetabulum |
-
1994
- 1994-03-03 GB GB9404077A patent/GB9404077D0/en active Pending
-
1995
- 1995-02-27 DK DK95909061T patent/DK0748193T3/en active
- 1995-02-27 WO PCT/GB1995/000403 patent/WO1995023566A1/en active IP Right Grant
- 1995-02-27 PT PT95909061T patent/PT748193E/en unknown
- 1995-02-27 AT AT95909061T patent/ATE209880T1/en not_active IP Right Cessation
- 1995-02-27 EP EP95909061A patent/EP0748193B1/en not_active Expired - Lifetime
- 1995-02-27 ES ES95909061T patent/ES2167416T3/en not_active Expired - Lifetime
- 1995-02-27 DE DE69524395T patent/DE69524395T2/en not_active Expired - Lifetime
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FR2134170A1 (en) * | 1971-04-23 | 1972-12-08 | Benoist Girard & Cie | |
FR2315903A1 (en) * | 1975-06-18 | 1977-01-28 | Sulzer Ag | ARTIFICIAL GLENOID CAVITY |
DE2742464A1 (en) * | 1977-09-21 | 1979-03-22 | Pfaudler Werke Ag | Internal body joint prosthesis - has socket sliding on ball on circular line of socket of larger radius |
FR2413078A1 (en) * | 1978-01-03 | 1979-07-27 | Serole Michelle | Hip prosthesis made of composite materials - has low wt. which assists swimming and can also be used for other body joints |
WO1986001394A1 (en) * | 1984-08-28 | 1986-03-13 | Rob. Mathys Co. | Artificial articular cavity for the hip with hydrostatic head support |
EP0226762A1 (en) * | 1985-11-18 | 1987-07-01 | GebràDer Sulzer Aktiengesellschaft | Artificial acetabular cup |
DE3630276A1 (en) * | 1986-09-05 | 1988-03-17 | Gernot Dr Med Felmet | Cementlessly implantable self-tensioning acetabular cup |
EP0302850A2 (en) * | 1987-07-09 | 1989-02-08 | Menschik, Alfred, Dr.med. | Artificial hip joint |
DE3840468A1 (en) * | 1988-12-01 | 1990-06-07 | Lieke Michael | Endoprosthetic components for an acetabulum |
Cited By (38)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1997016137A1 (en) * | 1995-10-31 | 1997-05-09 | Sarkisian James S | Prosthetic joint and method of manufacture |
US6059830A (en) * | 1995-11-02 | 2000-05-09 | Wright Medical Technology, Inc. | Low wear ball and cup joint prosthesis |
WO1997016138A1 (en) * | 1995-11-02 | 1997-05-09 | Wright Medical Technology, Inc. | Low-wear ball and cup joint prosthesis |
EP1340477A2 (en) * | 1996-04-12 | 2003-09-03 | Centerpulse Orthopedics Ltd. | Method for producing a bearing shell and a ball head of an artifical joint |
WO1997038650A1 (en) * | 1996-04-12 | 1997-10-23 | Sulzer Orthopädie Ag | Artificial joint, particularly an artificial hip joint |
EP1767170A2 (en) * | 1996-04-12 | 2007-03-28 | Zimmer GmbH | Method for producing a bearing shell and a ball head of an artifical joint |
US6126695A (en) * | 1996-04-12 | 2000-10-03 | Sulzer Orthopaedie Ag | Artificial joint, particularly an artificial hip joint |
EP1767170A3 (en) * | 1996-04-12 | 2012-04-04 | Zimmer GmbH | Method for producing a bearing shell and a ball head of an artifical joint |
EP1340477A3 (en) * | 1996-04-12 | 2005-11-16 | Centerpulse Orthopedics Ltd. | Method for producing a bearing shell and a ball head of an artifical joint |
US5928285A (en) * | 1997-05-30 | 1999-07-27 | Bristol-Myers Squibb Co. | Orthopaedic implant having an articulating surface with a conforming and translational surface |
EP1413266A1 (en) * | 1997-05-30 | 2004-04-28 | Bristol-Myers Squibb Company | Orthopaedic implant having an articulating surface with a conforming area surrounded by a translational area |
EP0998885A1 (en) * | 1997-05-30 | 2000-05-10 | Bristol-Myers Squibb Company | Orthopaedic implant having an articulating surface with a conforming area surrounded by a translational area |
AU755807B2 (en) * | 1998-11-05 | 2002-12-19 | Louis U. Bigliani | Orthopaedic implant having an articulating surface with a conforming and translational surface |
US6610097B2 (en) | 2000-03-15 | 2003-08-26 | Depuy Orthopaedics, Inc. | Prosthetic cup assembly which includes components possessing self-locking taper and associated method |
WO2002043626A1 (en) | 2000-12-01 | 2002-06-06 | Depuy International Limited | An orthopaedic joint prosthesis |
US7815685B2 (en) | 2000-12-01 | 2010-10-19 | Depuy International Ltd. | Orthopaedic joint prosthesis |
US7326253B2 (en) | 2001-11-16 | 2008-02-05 | Depuy Products, Inc. | Prosthetic cup assembly having increased assembly congruency |
AU2008237616B2 (en) * | 2001-12-19 | 2011-06-02 | Depuy Orthopaedics, Inc. | Prosthetic joints having reduced area bearing surfaces and application thereof to a range of sizes of prosthetic joints |
EP2108337A3 (en) * | 2001-12-19 | 2010-08-04 | Depuy Orthopaedics, Inc. | Prosthetic joints having reduced area bearing surfaces and application thereof to a range of sizes of prosthetic joints |
US7469474B2 (en) | 2002-01-17 | 2008-12-30 | Depuy International Limited | Manufacturing a component with a near spherical surface |
EP1767171A1 (en) * | 2005-09-23 | 2007-03-28 | Benoist Girard Sas | Prosthetic joints |
JP2007144129A (en) * | 2005-09-23 | 2007-06-14 | Benoist Girard Sas | Prosthetic joints |
AU2006220425B2 (en) * | 2005-09-23 | 2011-06-16 | Stryker European Holdings I, Llc | Prosthetic joints |
FR2904930A1 (en) * | 2006-08-18 | 2008-02-22 | Advanced Technical Fabrication | Double mobility acetabulum cup for hip prosthesis, has metallic inserting cup limited by hemispherical concave receiving surface that presents roughness parameter and out-of roundness, which are lower than specific micrometers |
US9566157B2 (en) | 2006-11-07 | 2017-02-14 | Biomedflex, Llc | Three-member prosthetic joint |
US9107754B2 (en) | 2006-11-07 | 2015-08-18 | Biomedflex, Llc | Prosthetic joint assembly and prosthetic joint member |
US9005306B2 (en) | 2006-11-07 | 2015-04-14 | Biomedflex, Llc | Medical Implants With Compliant Wear-Resistant Surfaces |
US9005307B2 (en) | 2006-11-07 | 2015-04-14 | Biomedflex, Llc | Prosthetic ball-and-socket joint |
EP1952786A3 (en) * | 2007-02-05 | 2008-08-13 | Depuy Products, Inc. | Aspherical hip bearing couple |
US8715364B2 (en) | 2007-02-05 | 2014-05-06 | DePuy Synthes Products, LLC | Aspheric hip bearing couple |
US8349018B2 (en) | 2007-02-23 | 2013-01-08 | Ceramtec Gmbh | Reduction of the development of stripe wear on inserts for hip joint prostheses by modifying the geometry of the transition between the face and spherical recess |
WO2008102014A1 (en) * | 2007-02-23 | 2008-08-28 | Ceramtec Ag | Reduction of the development of stripe wear on inserts for hip joint prostheses by modifying the geometry of the transition between the face and spherical recess |
US8652213B2 (en) | 2007-12-28 | 2014-02-18 | DePuy Synthes Products, LLC | Aspheric hip bearing couple |
US7985262B2 (en) | 2007-12-28 | 2011-07-26 | Depuy Products, Inc. | Aspheric hip bearing couple |
US9668864B2 (en) | 2007-12-28 | 2017-06-06 | DePuy Synthes Products, Inc. | Aspheric hip bearing couple |
US10245150B2 (en) | 2007-12-28 | 2019-04-02 | DePuy Synthes Products, Inc. | Method of implanting aspheric hip bearing couple |
US9445903B2 (en) | 2008-11-24 | 2016-09-20 | Biomet Manufacturing, Llc | Multi-bearing acetabular prosthesis |
US9445904B2 (en) | 2009-07-14 | 2016-09-20 | Biomet Manufacturing, Llc | Multiple bearing acetabular prosthesis |
Also Published As
Publication number | Publication date |
---|---|
DE69524395D1 (en) | 2002-01-17 |
DK0748193T3 (en) | 2002-03-11 |
ATE209880T1 (en) | 2001-12-15 |
EP0748193B1 (en) | 2001-12-05 |
PT748193E (en) | 2002-05-31 |
GB9404077D0 (en) | 1994-04-20 |
DE69524395T2 (en) | 2002-08-08 |
EP0748193A1 (en) | 1996-12-18 |
ES2167416T3 (en) | 2002-05-16 |
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